sale = 26.5
# 输入购买书的数量
quantity = input('购买书的数量:')
# 判断语句
if int(quantity) < 100:
    # 求总金额
    sum = sale * int(quantity)
    # 打印输出总金额
    print(sum)
# 判断语句
elif 100 <= int(quantity) < 500:
    # 求总金额
    sum = sale * int(quantity) * 0.9
    #打印输出总金额
    print(sum)
# 以上条件都不满足时执行
else:
    # 求总金额
    sum = sale * int(quantity) * 0.8-1000
    # 打印输出总金额
    print(sum)

